QPID-4775: Fix core dumps in HA tests introduced in r1478418

After this revision several of the tests in ha_tests.py were core dumping with 0
pointers in FieldTable entries in Queue::settings. It's not clear why the core
dumps were occuring nor why this patch fixes them. This patch eliminates a call
to the QueueSettings copy constructor, so something fishy going is on there.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1478632 13f79535-47bb-0310-9956-ffa450edef68